whether MAX2014 PWDN pin has any internal pull down resistor?

PWDN pin don’t have any internal pull down resistor, at PWDN pin input you should connect high value of resistor to GND for power down logic control input.

Can you provide the performance data of MAX2014 at 5MHz?

MAX2014 is a 50MHz to 1000MHz logarithmic RF detector. The test data of the MAX2014 at 5MHz is included in the attachment. It can still provide around 50-55dB of dynamic range at 5MHz. Slope is 47mV/dB at input between 0dBm and 5dbm input, and 24.62mV/dB at input between -60dBm and 65dBm.